LOW BIRTH WEIGHT IS ASSOCIATED WITH LOWER MEASURED GLOMERULAR FILTRATION RATE IN ADULT AGE

Abstract Background and Aims Low birth weight (LBW) has been shown to increase the risk of severe kidney disease. Studies have also shown that LBW is associated with lower estimated glomerular filtration rate (eGFR) or creatinine clearance in young adults. In the present study we investigated whether LBW associate with measured glomerular filtration rate (mGFR) in 40-50 year old adults. Method Retrospective longitudinal cohort study using the Medical Birth Registry of Norway to invite 200 individuals with LBW (birth weight ≤ 2300 gram) and 200 individuals with normal birth weight (NBW, 3500 – 4000 grams). All participants were aged 41 – 52 at time of examination. GFR was measured using plasma clearance of iohexol. Birth weight and gestational age were reported from the Medical Birth Registry. Main outcome was difference in measured GFR. Results We included 105 individuals – 57 LBW and 48 NBW – 55% females. Mean GFR was 94.8 ± 14.2 ml/min/1.73m2 in the LBW group and 100.2 ± 12.5 ml/min/1.73m2 in the NBW group (p=0.043). In females the mean GFR was 90.4 ± 12.2 ml/min/1.73m2 in the LBW group and 100.5 ± 14.0 ml/min/1.73m2 in the NBW group (p=0.005). In males the mean GFR was 101.4 ± 14.5 and 100 ± 11.2 ml/min/1.73m2 in the LBW and NBW groups respectively (p=0.7). In a multi-regression model adjusting for age, maternal age and maternal civil status, we found an increase in mGFR of 4.5 ml/min/1.73m2 for an increase of 1 kg in birth weight (p= 0.02) for women. For men there was a non-significant decrease of 1.2 ml/min/1.73m2 for an increase of 1 kg in birth weight (p=0.6). Conclusion Women aged 41-52 years with low birth weight had significantly lower measured GFR as compared with participants with normal birth weight, there was no difference for men.